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Posts Tagged ‘Stateless’

[Dynamics CE] – Strange Plug-in issue due to the usage of global variables

December 26, 2018 Leave a comment

Other day, one of my colleagues reported a plug-in issue which could not be reproduced consistently. All the troubleshooting options (i.e., Plug-in Profiler, Tracing) had been used but was unable to found the root cause.

On close retrospection of code, we found out the usage global variables in Plug-in class file, which made the Plug-in ‘Stateful’.

Due to this, issue could not be reproduced when tested with Plug-in Profiler as it creates single Plug-in instance. Issue will only be reproduced when concurrent users instantiate plug-ins.

You have to make sure to create your Plug-in as ‘Stateless’ to avoid issues during concurrent Plug-in execution.

What is ‘Stateful’ Plug-in?

  • If the Plug-in ‘Execute’ method refer any global variable(s), makes the Plug-in ‘Stateful’.

public class CustomersVirtual : IPlugin{

// ‘context’ variable declared as Global
IPluginExecutionContext context = null;
EntityCollection results = new EntityCollection();
public void Execute(IServiceProvider serviceProvider) {
context = (IPluginExecutionContext)serviceProvider.GetService(typeof(IPluginExecutionContext));

if (context.MessageName.ToLower() == “retrieve”){
Entity customer = new Entity(“raj_virtualcustomer”);
customer[“raj_customersid”] = Guid.NewGuid();
customer[“raj_name”] = “ABC Corporation”;

//add it to the collection
results.Entities.Add(customer);
}

In the above Plug-in sample, variables ‘context’ and ‘results’ been defined as global and referred in ‘Execute’ method which makes it ‘Stateful’

What is ‘Stateless’ Plug-in:

  • If the Plug-in ‘Execute’ method, has its own local variables and does not refer any global variables make the Plug-in ‘Stateless’.

public class CustomersVirtual : IPlugin{
public void Execute(IServiceProvider serviceProvider){

// ‘context’ variable declared as Local variable
IPluginExecutionContext context = (IPluginExecutionContext)
serviceProvider.GetService(typeof(IPluginExecutionContext));

EntityCollection results = new EntityCollection();

if (context.MessageName.ToLower() == “retrieve”)
{
Entity customer = new Entity(“raj_virtualcustomer”);
customer[“raj_customersid”] = Guid.NewGuid();
customer[“raj_name”] = “ABC Corporation”;

//add it to the collection
results.Entities.Add(customer);
}

In this sample, variables ‘context’ and ‘results’ been defined as Local in ‘Execute’ method which makes it ‘Stateless’

Why ‘Stateless’ Plug-in is recommended?

  • As per the design, Dynamics platform caches plug-in class instances and hence the constructor is not called for every invocation of plug-in execution.
  • IPlugins should be stateless is that multiple system threads could execute the same, shared, plug-in instance concurrently.
  • This opens up members of classes that implement IPlugin to potential thread-safety issues which could lead to data inconsistency or performance problems.
  • Read-only, static, and constant members are inherently thread-safe and can also be used reliably within a plug-in class.

How the Dynamics platform Caches Plug-in?

  • For performance reasons, Dynamics DOES NOT dispose of the object after it completes execution.
  • Dynamics caches the object and calls Execute on the same object instance on the next activation of the plug-in.
  • Certain operations, such as changing a plug-in’s registration properties, will trigger a notification to the platform to refresh the cache. In these scenarios, the plug-in will be reinitialized..
  • This means that you need to be very careful when defining class-level variables in the plug-in class as multiple threads can execute the code at one time

Bottom line:

  • Don’t use Global variables in Plug-ins

Refer below articles for more insights:

🙂

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Categories: CRM, Plug-Ins Tags: , ,